1. Field of the Invention
The present invention relates to an optical module on which at least two optical elements are mounted.
2. Description of Related Art
For an optical transmitter module for transmitting an a optical signal or an optical transmitter/receiver module for transmitting/receiving an optical signal, a technology has been proposed for mounting plural optical elements on the same substrate. As a processing speed of a transmission signal by the optical module increases, a crosstalk such that electromagnetic radiation generated from one of optical elements spreads to the other elements to interfere them may occur at the optical module.
A technology has been proposed to increase a distance between these elements to electrically reduce the crosstalk between the optical elements. For an optical transmitter module, a technology has been proposed to increase a distance between light-emitting elements (see article, “10 Gbps×4ch Parallel LD Module” by ANAGURA Masato, conference of Electronics Society in Institute of Electronics, Information and Communication Engineers, C-3-50, p. 160, 2001).
FIG. 1 shows a configuration of an optical transmitter module as related art, which has been disclosed in the article. The optical transmitter module 101A has an optical waveguide 102A in which cores 104A as curved waveguides and light-emitting elements 103 that are apart from each other. Increasing a distance between the adjacent light-emitting elements enables to be reduced a crosstalk between the elements. It is to be noted that a pitch between the light-emitting elements 103 is set to 1 mm.
Further, for an optical transmitter/receiver module, a technology has been proposed to increase a distance between a light-emitting element and a light-receiving element (see Japanese Patent Application Publication No. Hei 10-307238).
FIG. 2 shows a configuration of an optical a transmitter/receiver module as related art, which has been disclosed in the patent publication. The optical transmitter/receiver module 101B has an optical waveguide 102B, a light-emitting element 103, and a light-receiving element 105. The optical waveguide 102B includes a branching core 104B and also has, on its end face, a reflecting mirror 106 to fold back its optical path.
In an optical transmitter/receiver module, electromagnetic radiation generated on the side of a light-emitting element spreads to a light-receiving element to interfere it, which is then subject to any significant crosstalk on an electrical signal due to signal light. Thus, the optical transmitter/receiver module is more sensitive to the crosstalk than the optical transmitter module.
If the optical transmitter/receiver module has such a configuration that a light-emitting element and a light-receiving element that are parallel with each other are separated to an extent as to eliminate an influence of crosstalk, the curved waveguide becomes very long to increase its curvature, so that a module becomes very large. Therefore, in the optical transmitter/receiver module 101B as shown in FIG. 2, the light-emitting element 103 and the light-receiving element 105 are separated from each other so that the reflecting mirror 106 is provided on an end face of the waveguide 102B to fold back its optical path, thereby arranging these elements at the opposite ends of the optical waveguide 102B.